1. Field of Invention
The present invention relates to rotary engines as well as conventional piston engines having beneficial aspects of both. It is a hybrid combination of features that fundamentally operates as an Atkinson cycle four stroke utilizing the advantages of the Junkers opposed piston design. This design also implements rotary valves, similar to the Wankel engine. There are some prior art rotary engines which share similar elements, such as one disclosed by Albert which has a common combustion chamber with opposed pistons in which the cylinder is stationary, and others which have an elliptically shaped housing but do not incorporate the same features and are different in structure, operation, and advantages.
2. Description of the Prior Art
Most conventional internal combustion engines utilize a crankshaft to convert reciprocating piston motion into rotary motion. Also known as the crank-slider mechanism which had been commonly used prior to the advent of steam engines. This crank mechanism provided mobility to bicycles, spawned the industrial revolution as perfected by James Watt in the steam engine, and later propelled the automobile in the Otto cycle engine. Further developed by Lanchester, Daimler, Lenoir, and a host of well known and legions of unknown contributors in which a library of devoted work is attributed.
There are certain kinetic limitations to the crank mechanism. At the top and bottom segments of each stroke there is reduced leverage to perform work. There is no leverage at top dead center (TDC). An area of dwell exists for about thirty degrees where there is little or no motion provided to the piston. As the crankshaft rotates from TDC, leverage (gradually) increases from 0 (zero) to maximum leverage (from 60 to 120 degrees.) This area of maximum leverage is the “sweet spot” where most of the work is performed. Also toward the bottom of the stroke leverage is again progressively diminished. Under load, at lower engine speeds, combustion forces are constrained causing cylinder pressures to increase (spike), which can produce pre-ignition, resulting in knock that will lead to engine destruction. Higher-octane fuels are commonly used to retard combustion thus counteracting the moment of ignition until leverage is available.
The present invention provides a mechanism that produces a contiguous progression of leverage due to its mechanical linkage. Piston movement is continuous and more sinusoidal having less dwell at TDC and BDC. A larger torque arm provides more leverage to perform work producing a wider sweet spot. Also being a more balanced and efficient means of converting reciprocating motion into rotary motion than the crankshaft.
Various forms of the Otto cycle engine, derived from the crank-slider mechanism have resulted in engines with increased mechanical efficiency. The Diesel cycle engine utilizes a higher compression ratio to operate on low quality fuel that is harder to ignite but has higher energy content. Highly compressed air ignites the fuel as it is injected into the cylinder at TDC, which is known as compression ignition.
Another variation of the crank-slider is the Atkinson cycle engine, which increases mechanical efficiency by providing expanded strokes. A separate link between the crankshaft and the connecting rod varies the length of certain strokes, adjacent to less critical strokes. The expansion stroke is larger in volume than the compression stroke and is known to increase efficiency.
An opposed piston design pre-dating WWII by Hugo Junkers operating as a diesel 2-cycle engine proved the benefits of eliminating the cylinder heads, which were prone to crack and even today are a substantial cause of engine failure. Having opposed pistons reduces heat transfer and permits much higher operating temperatures and pressures than otherwise possible. Each piston is connected to separate crankshafts and synchronized slightly out of phase to allow scavenging through intake and exhaust ports in the common cylinder. Additional benefits of the opposed piston (O-P) design are, combustion forces are transferred equally through opposed pistons and more closely duplicates the natural model of combustion. Equilateral pressures force the pistons apart in both directions, and the flame front does not have to travel as far down the cylinder. The main bearings, piston pins, connecting rods, and associated parts absorb fewer stresses from combustion related forces.
The Hybrid Piston/Rotary engine as disclosed provides similar mechanical advantages to these previous designs without the mechanical complexities while reducing the number of parts and is more compact.
Another variation providing an alternative mechanism to the crank-slider is the Scotch yoke mechanism (Bourke engine). This mechanism increases dwell time at TDC and BDC, which is thought to increase mechanical efficiency. There are two schools of thought as to which is preferable. To dwell or not to dwell. Another is the Geneva stop (Maltese cross) mechanism as well as the swash plate mechanism. None of these contrivances are in wide use today or had any success in engines.
The Wankel rotary engine is conventionally different, having a triangular rotor and elliptical housing instead of pistons and a traditional cylinder. It utilizes a simplified rotary valve, which reduces parasitic frictional losses and permits higher revving output while providing all four strokes in a single rotation of the takeoff shaft. Instead of a crankshaft, a three lobed rotor oscillates trichoidally to forcibly gyrate an eccentric shaft, which is the power shaft.
Several rotary engines have opposed pistons, including a design by Albert, which has an elliptical housing that rotates around a stationary common cylinder. The pistons are connected to rollers but do not provide a valid method for retracting the pistons during the intake stroke. Designs by Murray provide a rotating block of multiple cylinders without opposed pistons but has rotary valves and air-cooling. The pistons are connected to rollers on cam followers, which are retracted centrifugally by counter weights.
The Hybrid Piston/Rotary engine utilizes rotary valves similar to the Wankel rotary engine. It provides four distinct strokes every revolution of the rotor shaft with the expanded strokes of the Atkinson design. It has opposed pistons similar to the Junkers engine that eliminates the need for a cylinder head. Both pistons distribute cylinder pressures equally and each piston shares half the pressure of combustion. By providing a more efficient mechanism than the crankshaft, it provides a continuous sinusoidal motion to the pistons. Utilizing the benefits of current piston engine technology while improving combustion by turbulent vortex mixing.